SAT Subject Physics Practice Question 50: Answer and Explanation

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Question: 50

7. A satellite is currently orbiting Earth in a circular orbit of radius R; its kinetic energy is K1. If the satellite is moved and enters a new circular orbit of radius 2R, what will be its kinetic energya?

C. K1
D. 2K1
E. 4K1

Correct Answer: B


The gravitational pull by the earth provides the centripetal force on the satellite, so . This gives , so the kinetic energy K of the satellite is inversely proportional to R. Therefore, if R increases by a factor of 2, then K decreases by a factor of 2.

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